2015-03-03T16:59:46ZTrophic structure of the bathyal benthos at an area with evidence of methane seep activity off southern Chile (∼45°S)http://hdl.handle.net/1957/55253
Trophic structure of the bathyal benthos at an area with evidence of methane seep activity off southern Chile (∼45°S)
Zapata-Hernández, Germán; Sellanes, Javier; Thurber, Andrew R.; Levin, Lisa A.
Through application of carbon (C) and nitrogen (N) stable isotope analyses, we investigated the benthic trophic structure of
the upper-slope off southern Chile (~45°S) including a recent methane seep area discovered as part of this study. The observed
fauna comprised 53 invertebrates and seven fish taxa, including remains of chemosymbiotic fauna (e.g. chemosymbiotic
bivalves and siboglinid polychaetes), which are typical of methane seep environments. While in close-proximity to a seep,
the heterotrophic fauna had a nutrition derived predominantly from photosynthetic sources (δ¹³C > -21‰). The absence
of chemosynthesis-based nutrition in the consumers was likely a result of using an Agassiz trawl to sample the benthos, a
method that is likely to collect a mix of fauna including individuals from adjacent non-seep bathyal environments. While
four trophic levels were estimated for invertebrates, the fish assemblage was positioned within the third trophic level of the
food web. Differences in corrected standard ellipse area (SEA[subscript C]), which is a proxy of the isotopic niche width, yielded differences
for the demersal fish Notophycis marginata (SEA[subscript C] = 5.1‰) and Coelorinchus fasciatus (SEA[subscript C] = 1.1‰), suggesting distinct trophic behaviours. No ontogenic changes were detected in C. fasciatus regarding food sources and trophic position. The
present study contributes the first basic trophic data for the bathyal area off southern Chile, including the identification of
a new methane seep area, among the furthest south ever discovered. Such information provides the basis for the proper sustainable
management of the benthic environments present along the vast Chilean continental margin.
This is the publisher’s final pdf. The published article is copyrighted by the Marine Biological Association of the United Kingdom and can be found at: http://journals.cambridge.org/action/displayJournal?jid=MBI.
2014-06-01T00:00:00ZAcceptance, Acceptability, and Trust for Sagebrush Restoration Options in the Great Basin: A Longitudinal Perspectivehttp://hdl.handle.net/1957/55252
Acceptance, Acceptability, and Trust for Sagebrush Restoration Options in the Great Basin: A Longitudinal Perspective
Gordon, Ryan; Brunson, Mark W.; Shindler, Bruce
In surveys of residents in three urban and three rural locations in the Great Basin we examined the social acceptability of six
management practices showing promise for restoring sagebrush-dominated rangelands. Unlike most studies of range
management perceptions that have relied on single measurements, we used longitudinal data from a questionnaire mailed in
2006 to residents that were resurveyed in 2010. Overall, 698 respondents comprised the panel. Respondents’ self-reported levels
of knowledge about the health and management of Great Basin rangelands decreased from 2006 to 2010. In both years, mean
acceptance was greater for the use of prescribed fire, grazing, felling, and mowing, but relatively low for chaining and herbicide
use. Overall, acceptability ratings were similar in 2006 and 2010 but individually about half of the acceptance responses differed
between years. Practices were more acceptable to respondents who expressed greater concern about threats posed by inaction,
except that the threat of wildfire was negatively associated with acceptance for prescribed burning. Acceptance was not
significantly related to concern about overall health of Great Basin rangelands, or to self-reported knowledge level. Rural/urban
residence and general attitudes toward environmental protection were sometimes influential, but more so in 2006 than in 2010.
By far the best predictor of acceptance was trust in agencies’ ability to implement the practice. In both years respondents were
more likely to judge a practice acceptable than to trust agencies to use the practice. Positive or negative change in trust level was
the most significant predictor of change in acceptability judgment from 2006 to 2010. Results suggest that efforts to increase
acceptance of practices among Great Basin stakeholders should focus on activities designed to build trust rather than simply
providing more or better information.
This is the publisher’s final pdf. The published article is copyrighted by Society for Range Management and can be found at: http://www.srmjournals.org/; The SageSTEP project paid for open access to this article at the time of its publication.
2014-09-01T00:00:00ZParabolic northern-hemisphere river flow teleconnections to El Niño-Southern Oscillation and the Arctic Oscillationhttp://hdl.handle.net/1957/55251
Parabolic northern-hemisphere river flow teleconnections to El Niño-Southern Oscillation and the Arctic Oscillation
Fleming, S. W.; Dahlke, H. E.
It is almost universally assumed in statistical hydroclimatology that relationships between large-scale
climate indices and local-scale hydrometeorological responses, though possibly nonlinear,
are monotonic. However, recent work suggests that northern-hemisphere atmospheric
teleconnections to El Niño-Southern Oscillation (ENSO) and the Arctic Oscillation can be
parabolic. The effect has recently been explicitly confirmed in hydrologic responses, though
associations are complicated by land surface characteristics and processes, and investigation of
water resource implications has been limited to date. Here, we apply an Akaike Information
Criterion-based polynomial selection approach to investigate annual flow volume
teleconnections for 42 of the northern hemisphere’s largest ocean-reaching rivers. Though we
find a rich diversity of responses, parabolic relationships are formally consistent with the data for
almost half the rivers, and the optimal model for eight. These highly nonlinear water supply
teleconnections could radically alter the standard conceptual model of how water resources
respond to climatic variability. For example, the Sacramento river in drought-ridden California
exhibits no significant monotonic ENSO teleconnection but a 0.92 probability of a quadratic
relationship, reducing mean predictive error by up to 65% and suggesting greater opportunity for
climate index-based water supply forecasts than previously appreciated.
This is the publisher’s final pdf. The published article is copyrighted by the Institute of Physics Publishing and can be found at: http://iopscience.iop.org/1748-9326.
2014-10-08T00:00:00ZMechanism reduction for multicomponent surrogates: A case study using toluene reference fuelshttp://hdl.handle.net/1957/55250
Mechanism reduction for multicomponent surrogates: A case study using toluene reference fuels
Niemeyer, Kyle E.; Sung, Chih-Jen
Strategies and recommendations for performing skeletal reductions of multicomponent surrogate fuels are presented, through the generation and validation of skeletal mechanisms for a three-component toluene reference fuel. Using the directed relation graph with error propagation and sensitivity analysis method followed by a further unimportant reaction elimination stage, skeletal mechanisms valid over comprehensive and high-temperature ranges of conditions were developed at varying levels of detail. These skeletal mechanisms were generated based on autoignition simulations, and validation using ignition delay predictions showed good agreement with the detailed mechanism in the target range of conditions. When validated using phenomena other than autoignition, such as perfectly stirred reactor and laminar flame propagation, tight error control or more restrictions on the reduction during the sensitivity analysis stage were needed to ensure good agreement. In addition, tight error limits were needed for close prediction of ignition delay when varying the mixture composition away from that used for the reduction. In homogeneous compression-ignition engine simulations, the skeletal mechanisms closely matched the point of ignition and accurately predicted species profiles for lean to stoichiometric conditions. Furthermore, the efficacy of generating a multicomponent skeletal mechanism was compared to combining skeletal mechanisms produced separately for neat fuel components; using the same error limits, the latter resulted in a larger skeletal mechanism size that also lacked important cross reactions between fuel components. Based on the present results, general guidelines for reducing detailed mechanisms for multicomponent fuels are discussed.
This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/combustion-and-flame/
2014-11-01T00:00:00Z